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Hot water being cooled by standing ground water???

Our main bathroom is approx 40 feet from the hot water tank. House is on a slab, well & septic. After heavy rains the water in this bathroom is lukewarm. My theory is that the hot water pipes are surrounded by cold groundwater, thus cooling it before it reaches its destination. My husband disagrees, assuming the pressure of the water would move it along fast enough that it would not cool this much. Does anyone have another theory or solution?

Re: Hot water being cooled by standing ground water???

That sounds like a really LONG WAY for hot water to travel thru the pipes from the hot water tank to the bathroom; are you saying the pipes are buried under the slab, and there is no HW recirculation device installed to keep the water to the bathroom hot???

Perhaps moving the HW tank closer to the bathroom might work, assuming there is space for it there????

Re: Hot water being cooled by standing ground water???

I think you are right. Water can transfer a lot of heat quickly, that is why it is used to cool the engine in your car or truck. I'll bet that on good days, when you shut off the hot water in the bathroom, it will be stone cold if you turn it back on after only a few minutes.

Re: Hot water being cooled by standing ground water???

In my experience, the pipes would be routed in the slab and if there is that much water against the slab causing the heat loss, you may have a more pressing issue with the slab & foundation being possibly undermined by water. Check the grading to be sure there is positive flow away from the house.
While 40' is a pretty long run, the fact that the problem only occurs after heavy rains is a clue something is wrong.